Our major objective is to define the molecular mechanisms of action of the E. coli enterotoxin. Using Y1 adrenal cells in tissue culture as the model system, we hope to characterize the toxin's receptor site and ligands responsible for binding. We plan to also compare the binding sites of E. coli toxin with those for cholera toxin through competition experiments. Additional objectives center around seroepidemiologic investigations of defined populations, and the control of enterotoxin synthesis by bacteria.